The present disclosure relates to marking microelectronic devices having a microelectronic die including an integrated circuit; more particularly, several aspects of the invention are related to marking packaged microelectronic devices and bare dies used in microelectronic devices.
Microelectronic devices, such as memory devices and microprocessors, typically include a microelectronic die or chip encased in a plastic, ceramic or metal protective covering. The die can include memory cells, processor circuits, interconnecting circuitry and/or other functional features. The die also typically includes an array of very small bond pads electrically coupled to the functional features. When the die is packaged, the bond pads are coupled to leads, solder ball pads or other types of terminals for operatively coupling the microelectronic dies to buses, circuits and/or other microelectronic devices.
Several different techniques have been developed for packaging microelectronic dies. The dies, for example, can be incorporated into individual protective packages, mounted with other components in a hybrid or multiple chip modules, or connected directly to a printed circuit board. When a die is incorporated into an individual protective package, the bond pads on the die are typically coupled to a lead frame and the die is covered or otherwise sealed from the environment. When the die is directly attached to a printed circuit board or another type of substrate, the bond pads on the die are typically coupled to corresponding pads on the substrate using wire bonds, ball grid arrays and other techniques. Such dies that are mounted directly to a substrate are then covered with a plastic, ceramic or other protective material. The dies that are mounted directly to the substrates are generally called Chip Scale Package (CSP) devices and Flip Chip Bare Die devices with solder balls directly attached to a substrate.
Microelectronic device manufacturers typically fabricate a plurality of dies on a wafer and then cut the wafer to separate the dies from one another. After fabricating the dies, manufacturers generally perform additional operations in which they handle and test (a) wafers having a plurality of dies, (b) individual dies after they have been singulated, and (c) the packaged dies. The basic operations that a manufacturer performs after fabricating the dies include backside preparation, die separation, die picking, die inspection, die attachment, wire bonding or flip-chip attachment, preseal inspection, package sealing, plating, trimming, final tests, and other procedures. Throughout several of these procedures the individual dies and the packaged dies are marked with fiducials and identification marks because many of the procedures for packaging the dies are performed by machines that use machine-vision technology to identify and accurately position the dies. Therefore, the fiducials and the identification marks should accordingly be clear, well-defined marks that can be accurately recognized by the machine-vision equipment.
Conventional marking systems for marking bare dies include a laser that changes the color of the silicon on the backside of a die. One conventional marking system specifically uses a laser having a wavelength of 1,064 nm, but other marking procedures alternatively use lasers with a wavelength of 532 nm. Conventional marking systems that use lasers to change the color of the silicon may have many drawbacks.
One drawback of conventional laser marking systems is that the marks on the silicon may not have sufficient clarity to be accurately recognized by the machine vision equipment. As a result, machine-vision devices may not accurately identify or position the dies during a processing operation. Conventional marking systems may accordingly inhibit the processing equipment from effectively working on a die or a package.
Another drawback of conventional laser marking systems is that the lasers may damage the dies. At least one microelectronic device manufacturer has determined that a 1,064 nm laser may damage the integrated circuits on certain dies. Additionally, if other wavelengths of radiation are operated at higher power settings to produce darker mark then these lasers may also damage the integrated circuitry. Therefore, conventional laser marking systems may damage the dies at the very end of the fabricating process after a considerable amount of time and money has been expended to produce the dies.
Still another drawback of conventional laser marking systems is that it is time consuming to mark bare silicon dies as well as packaged devices. In a typical application, a laser may make the marks at a xe2x80x9cscan ratexe2x80x9d of a few hundred millimeters per second. Although such scan rates are relatively quick, it may still require a significant amount of time to mark a large number of dies. Therefore, conventional laser marking systems may become a bottleneck for processing and packaging finished dies.
The present invention is directed toward marking microelectronic devices, such as bare microelectronic dies and packaged devices, to identify and handle wafers, bare dies and packaged devices. In one embodiment, a microelectronic device includes a first exterior surface, a second exterior surface having a contact array with a plurality of contacts, and an integrated circuit coupled to the contacts. The microelectronic device can further include a marking medium applied to the first exterior surface of the device. In one embodiment, the marking medium includes a contrast film section having an underlying contrast film applied to the first exterior surface and an outer contrast film attached to the underlying contrast film. In another embodiment, the marking medium can include a contrast film section having only an outer contrast film applied to the first exterior surface of the device. The outer contrast film can have a high optical contrast with respect to the underlying contrast film or the first exterior surface of the device, and the outer contrast film can be changed by a selected radiation so that a portion of the outer contrast film can be selectively removed from the device. The marking medium can optionally include a transfer medium attached to the contrast film section.
Several embodiments of the invention are directed toward methods of marking a microelectronic device having a microelectronic die including an integrated circuit. In one embodiment, a marking method can include applying a marking medium to a surface on either the microelectronic die or a package that encases the microelectronic die. The marking medium can have an outer contrast film that has a high optical contrast with respect to a material immediately under the outer contrast film. This embodiment of the method can also include selectively removing a portion of the outer contrast film to leave a patterned portion on the microelectronic device. The patterned portion of the outer contrast film that is left on the microelectronic device and the material immediately under the outer contrast film define a mark on the microelectronic device.